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In Reply to: Bias on Manley Snappers posted by fin1bxn@msn.com on February 16, 2017 at 06:42:10:
You got 6CA7s that are too hot (hot = higher current under a given set of operating conditions). Your amp does not have sufficient bias adjustment range to bring the current down to spec. There is nothing wrong with the tubes per se - they are just a misfit for the amp.
You need a set of 6CA7s that are mid range to cool biasing (cool = lower current under a given set of operating conditions). Then you'll be able to adjust the bias to the specified range.
Yes it IS a problem that the 2 tubes are at .416! That is roughly 30% over the spec for the amp.
And finally the .416 is NOT current (ma.) It is VOLTAGE!! It's the voltage developed across a 10 Ohm resistor in the circuit between the tube cathode and ground by the current flowing through the tube and on through the resistor. Using Ohm's Law you can compute the current. The current equals the voltage (.416 volts) divided by the resistance (10 Ohms) which equals .0416 or 41.6 milliamps (abbreviated ma.)
If you own a tube amp it behooves you to learn about bias and biasing so you don't get confused by it.
BTW - what brand 6CA7s are you using?
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Follow Ups
- RE: Bias on Manley Snappers - Jim McShane 13:47:59 02/16/17 (6)
- RE: Bias on Manley Snappers - Had tubes tested - fin1bxn@msn.com 05:32:25 03/07/17 (0)
- RE: Bias on Manley Snappers- your right - fin1bxn@msn.com 13:58:29 02/16/17 (4)
- RE: Bias on Manley Snappers- your right - Jim McShane 14:35:33 02/16/17 (3)
- RE: Bias on Manley Snappers- your right - fin1bxn@msn.com 03:59:58 02/17/17 (1)
- Snapper output tube story - M3 lover 10:21:26 02/17/17 (0)
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